CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDER’S EQUITY Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Subsidiaries [Member]	Subsidiaries [Member] Common Stock [Member]	Subsidiaries [Member] Additional Paid-in Capital [Member]	Subsidiaries [Member] Retained Earnings [Member]	Subsidiaries [Member] AOCI Attributable to Parent [Member]
Beginning Balance (in shares) at Dec. 31, 2020		200					85,903,791
Beginning Balance at Dec. 31, 2020	$ 4,139,882	$ 0	$ 3,313,532	$ 912,787	$ (86,437)	$ 4,181,409	$ 859	$ 3,485,105	$ 876,401	$ (180,956)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	188,993			188,993		199,470			199,470
Dividends, Common Stock	(22,939)			(22,939)		(52,053)			(52,053)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2,385				2,385	4,554				4,554
Ending Balance (in shares) at Mar. 31, 2021		200					85,903,791
Ending Balance at Mar. 31, 2021	4,308,321	$ 0	3,313,532	1,078,841	(84,052)	4,333,380	$ 859	3,485,105	1,023,818	(176,402)
Beginning Balance (in shares) at Dec. 31, 2020		200					85,903,791
Beginning Balance at Dec. 31, 2020	4,139,882	$ 0	3,313,532	912,787	(86,437)	4,181,409	$ 859	3,485,105	876,401	(180,956)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	293,804					351,959
Ending Balance (in shares) at Sep. 30, 2021		200					85,903,791
Ending Balance at Sep. 30, 2021	4,581,998	$ 0	3,523,532	1,138,524	(80,058)	4,375,486	$ 859	3,485,105	1,057,515	(167,993)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Investment from Parent	210,000					0
Beginning Balance (in shares) at Mar. 31, 2021		200					85,903,791
Beginning Balance at Mar. 31, 2021	4,308,321	$ 0	3,313,532	1,078,841	(84,052)	4,333,380	$ 859	3,485,105	1,023,818	(176,402)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	55,242			55,242		78,364			78,364
Dividends, Common Stock	(23,214)			(23,214)		(44,622)			(44,622)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2,386				2,386	4,555				4,555
Ending Balance (in shares) at Jun. 30, 2021		200					85,903,791
Ending Balance at Jun. 30, 2021	4,552,735	$ 0	3,523,532	1,110,869	(81,666)	4,371,677	$ 859	3,485,105	1,057,560	(171,847)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Investment from Parent	210,000		210,000
Net Income (Loss) Attributable to Parent	49,569			49,569		74,125			74,125
Dividends, Common Stock	(21,914)			(21,914)		(74,170)			(74,170)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,608				1,608	3,854				3,854
Ending Balance (in shares) at Sep. 30, 2021		200					85,903,791
Ending Balance at Sep. 30, 2021	$ 4,581,998	$ 0	3,523,532	1,138,524	(80,058)	$ 4,375,486	$ 859	3,485,105	1,057,515	(167,993)
Beginning Balance (in shares) at Dec. 31, 2021	200	200				85,903,791	85,903,791
Beginning Balance at Dec. 31, 2021	$ 4,563,316	$ 0	3,523,532	1,067,216	(27,432)	$ 4,355,430	$ 859	3,485,105	982,607	(113,141)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	278,295			278,295		288,081			288,081
Dividends, Common Stock	(939)			(939)		(13,896)			(13,896)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,831				1,831	3,685				3,685
Ending Balance (in shares) at Mar. 31, 2022		200					85,903,791
Ending Balance at Mar. 31, 2022	$ 4,842,503	$ 0	3,523,532	1,344,572	(25,601)	$ 4,633,300	$ 859	3,485,105	1,256,792	(109,456)
Beginning Balance (in shares) at Dec. 31, 2021	200	200				85,903,791	85,903,791
Beginning Balance at Dec. 31, 2021	$ 4,563,316	$ 0	3,523,532	1,067,216	(27,432)	$ 4,355,430	$ 859	3,485,105	982,607	(113,141)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	$ 151,089					$ 213,950
Ending Balance (in shares) at Sep. 30, 2022	200	200				85,903,791	85,903,791
Ending Balance at Sep. 30, 2022	$ 4,719,721	$ 0	3,523,532	1,217,063	(20,874)	$ 4,611,052	$ 859	3,535,105	1,176,125	(101,037)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Investment from Parent	0					50,000
Beginning Balance (in shares) at Mar. 31, 2022		200					85,903,791
Beginning Balance at Mar. 31, 2022	4,842,503	$ 0	3,523,532	1,344,572	(25,601)	4,633,300	$ 859	3,485,105	1,256,792	(109,456)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	(33,496)			(33,496)		(6,318)			(6,318)
Dividends, Common Stock	(294)			(294)		(2,037)			(2,037)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,831				1,831	3,685				3,685
Ending Balance (in shares) at Jun. 30, 2022		200					85,903,791
Ending Balance at Jun. 30, 2022	4,810,544	$ 0	3,523,532	1,310,782	(23,770)	4,628,630	$ 859	3,485,105	1,248,437	(105,771)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	(93,710)			(93,710)		(67,813)			(67,813)
Dividends, Common Stock	(9)			(9)		(4,499)			(4,499)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 2,896				2,896	$ 4,734				4,734
Ending Balance (in shares) at Sep. 30, 2022	200	200				85,903,791	85,903,791
Ending Balance at Sep. 30, 2022	$ 4,719,721	$ 0	$ 3,523,532	$ 1,217,063	$ (20,874)	$ 4,611,052	$ 859	3,535,105	$ 1,176,125	$ (101,037)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Investment from Parent						$ 50,000		$ 50,000